maria-developers team mailing list archive

[Sergei Golubchik <serg@xxxxxxxxxxx>]

Hi, Michael!

On Sep 08, Michael Widenius wrote:
> revision-id: c3ecf0d6243 (mariadb-10.5.2-269-gc3ecf0d6243)
> parent(s): c79c6f78205
> author: Michael Widenius <michael.widenius@xxxxxxxxx>
> committer: Michael Widenius <michael.widenius@xxxxxxxxx>
> timestamp: 2020-09-02 20:58:33 +0300
> message:
> 
> Optimize size of lex structures
> 
> LEX, st_select_lex, st_select_unit optimized for space:
> - Use bit fields for bool variables
> - Ensure that all bit fields are initialized (improves
>   performance for init functions as all bit fields can be
>   initalized with one memory access)
> - Move members around in above structures to remove alignment
>   gaps
> 
> diff --git a/sql/sql_lex.h b/sql/sql_lex.h
> index f516219c01a..1f6e50d8b60 100644
> --- a/sql/sql_lex.h
> +++ b/sql/sql_lex.h
> @@ -725,12 +725,15 @@ class st_select_lex_node {
>    st_select_lex_node *next, **prev,   /* neighbor list */
>      *master, *slave,                  /* vertical links */
>      *link_next, **link_prev;          /* list of whole SELECT_LEX */
> +  enum sub_select_type linkage;
>  
>    void init_query_common();
> -public:
>  
> +public:
>    ulonglong options;
> -
> +  uint8 uncacheable;
> +  bool distinct:1;
> +  bool no_table_names_allowed:1; /* used for global order by */

I thought you didn't like this approach and preferred

  flags & DISTINCT

instead. Either you forgot to change LEX to flags or you forgot to
squash your commits.

>    /*
>      result of this query can't be cached, bit field, can be :

Regards,
Sergei
VP of MariaDB Server Engineering
and security@xxxxxxxxxxx